The conventional surface protective layer and interlayer insulating layer for a semiconductor device includes a polyimide resin which can have excellent heat resistance, electrical properties, and mechanical properties.
The polyimide resin has recently been used as a photosensitive polyimide precursor composition which can be coated easily. The photosensitive polyimide precursor composition is coated on a semiconductor device, patterned by ultraviolet (UV) rays, developed, and heat imidized, to easily provide a surface protective layer, an interlayer insulating layer, and the like. Accordingly, it is possible to shorten the processing time compared with that of a conventional non-photosensitive polyimide precursor composition.
The photosensitive polyimide precursor composition can be applied as a positive type in which an exposed part is dissolved by development, or a negative type in which the exposed part is cured and maintained. Positive type compositions can be developed by a non-toxic alkali aqueous solution. The positive photosensitive polyimide precursor composition can include a polyimide precursor of polyamic acid, a photosensitive material of diazonaphthoquinone, and the like. However, it can be difficult to obtain a desired pattern using the positive photosensitive polyimide precursor composition because the carboxylic acid of the polyamic acid is too highly soluble in an alkali.
In order to solve this problem, a material to which a phenolic hydroxyl group has been introduced instead of carboxylic acid by esterifying polyamidic acid with an alcohol compound having at least one hydroxyl group has been proposed, but this material is insufficiently developed, causing problems of film loss or resin delamination from the substrate.
Recently, a material in which a polybenzoxazole precursor is mixed with a diazonaphthoquinone compound has drawn attention, but when the polybenzoxazole precursor composition is actually used, film loss of an unexposed part can be significantly increased, so it is difficult to obtain a desirable pattern after the developing process.
In order to improve this, if the molecular weight of the polybenzoxazole precursor is increased, the film loss amount of the unexposed part is reduced, but development residue (scum) is generated, so resolution may be decreased and the development duration on the exposed part may be increased.
In order to solve this problem, film loss may be suppressed in non-exposed parts during development by adding a certain phenol compound to a polybenzoxazole precursor composition. However, the effect of suppressing the film loss of the unexposed part is insufficient. Accordingly, there is still a need to increase the effects on suppressing film loss, along with preventing generation of the development residue (scum).
Furthermore, when this polyimide or polybenzoxazole precursor composition is prepared into a thermally cured film, the thermally cured film should have excellent mechanical properties such as tensile strength and elongation because it can remain in a semiconductor device as a surface protective layer. However, generally-used polyimide or polybenzoxazole precursors tend to have inappropriate mechanical properties, and in particular, elongation, and also have poor heat resistance.
In order to solve this problem, it has been reported that various additives can be added thereto or a precursor compound that is cross-linkable during the thermal curing can be used. However, while such compounds could improve mechanical properties, and in particular elongation, they could not accomplish optical properties such as sensitivity, resolution, and the like. Accordingly, there is still a need for research directed to methods that can attain excellent mechanical properties without deteriorating these optical properties.